IPoIB: improve IPv4/IPv6 to IB mcast mapping functions

An IPoIB subnet on an IB fabric that spans multiple IB subnets can't
use link-local scope in multicast GIDs.  The existing routines that
map IP/IPv6 multicast addresses into IB link-level addresses hard-code
the scope to link-local, and they also leave the partition key field
uninitialised.  This patch adds a parameter (the link-level broadcast
address) to the mapping routines, allowing them to initialise both the
scope and the P_Key appropriately, and fixes up the call sites.

The next step will be to add a way to configure the scope for an IPoIB
interface.

Signed-off-by: Rolf Manderscheid <rvm@obsidianresearch.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/include/net/ip.h b/include/net/ip.h
index 840dd91b513b..50c8889b1b8d 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -266,20 +266,22 @@ static inline void ip_eth_mc_map(__be32 naddr, char *buf)
  *      Leave P_Key as 0 to be filled in by driver.
  */
 
-static inline void ip_ib_mc_map(__be32 naddr, char *buf)
+static inline void ip_ib_mc_map(__be32 naddr, const unsigned char *broadcast, char *buf)
 {
         __u32 addr;
+        unsigned char scope = broadcast[5] & 0xF;
+
         buf[0]  = 0;            /* Reserved */
         buf[1]  = 0xff;         /* Multicast QPN */
         buf[2]  = 0xff;
         buf[3]  = 0xff;
         addr    = ntohl(naddr);
         buf[4]  = 0xff;
-        buf[5]  = 0x12;         /* link local scope */
+        buf[5]  = 0x10 | scope; /* scope from broadcast address */
         buf[6]  = 0x40;         /* IPv4 signature */
         buf[7]  = 0x1b;
-        buf[8]  = 0;            /* P_Key */
-        buf[9]  = 0;
+        buf[8]  = broadcast[8];         /* P_Key */
+        buf[9]  = broadcast[9];
         buf[10] = 0;
         buf[11] = 0;
         buf[12] = 0;